Here is the full list of all 51 Red Dead Redemption 2 achievements. It takes around 200 hours to unlock all of the achievements on Windows.
Red Dead Online: Concurrently own 5 horses.
Red Dead Online: Achieve MVP 3 times (in a round with at least 4 players).
Red Dead Online: Successfully counter a rival Posse's Free Roam mission.
Red Dead Online: Complete a Free Roam mission as part of a Posse with at least 2 members.
Study every animal across all states in Story Mode.
Survive 3 days holding a bounty of $250 in all states.
Survive 18 bear attacks and kill the bear each time in Story Mode.
Red Dead Online: Craft 25 pieces of ammunition.
Red Dead Online: Craft 20 items (excluding ammo).
Red Dead Online: Purchase 5 camp improvements.
Red Dead Online: Reach Rank 50.
Red Dead Online: Accept 10 Free Roam missions from characters around the world.
Red Dead Online: Form a Persistent Posse.
Red Dead Online: Achieve 5 gold belt buckles from awards.
Red Dead Online: Play 5 Free Roam Events.
Red Dead Online: Pick 25 Herbs.
Red Dead Online: Sell 20 items to the Butcher.
Red Dead Online: Reach Rank 10.
Red Dead Online: Take part in a Series.
Find a permanent home for the squirrel statue.
Attain 100% completion.
Skin every species of animal in Story Mode.
Red Dead Online: Complete the Intro.
Find the graves of each of your fallen companions.
Complete all optional Honor story missions.
Earn 70 Gold Medals in Story missions.
Catch a fish weighing at least 16 lbs (7.3 kg).
Complete the Epilogue.
Reach maximum or minimum Honor level.
Complete 'A New Jerusalem'.
Complete 'Red Dead Redemption'.
Complete a Companion Activity in each camp.
Discover the fate of Marko Dragic.
Spend $5000 across all shops.
Complete 10 Stranger mission strands.
Complete one of the Collectable strands.
Complete 'Goodbye, Dear Friend'.
Complete Chapter 5.
Complete Chapter 4.
Complete Chapter 3.
Play all mini games.
Deliver 5 camp companion item requests.
Craft 30 unique items in Story Mode.
Recover the stash from 4 homesteads.
Rob or loot $250.
Complete Chapter 2.
Donate $250 to the gang tithing box.
Reach max bonding level with a horse.
Upgrade each available component for a single sidearm or longarm weapon.
Complete Chapter 1.
Complete 'Enter, Pursued by a Memory'.